Hello all. I am wondering if anyone can pass along any comparative impressions of the three scopes noted in the subject line - a Pentax J80 f/12, an Antares 90mm f/11 "Vixen spec", and an Orion 100ed f/9.

I am making a bit of a reorientation and am adding some refractors to my scope stable. I currently use an 8" dob, but just bought the 90mm Antares, and am in a position to maybe get both of the other scopes (though maybe just one). The Pentax is more of a collectible purchase (in my view anyway - there is something about the idea of a classic Pentax refractor that is just neat). And the Orion is an attempt to get one of the best bang-for-the-buck apo's (not splitting hairs - I am sure it is close enough for my purposes).

I don't have much refractor viewing experience (which probably makes the idea if buying 3 seem odd), but there are a couple of opportunities that make it fairly reasonable.

I am mainly a planetary/lunar viewer - especially with these scopes. I am wondering if anyone has any comments about their relative performance, quirks, etc.

The Orion ED100 [and its clones] with FPL-53 glass are one of the best cost effective planetary and lunar scopes you can get. I have had the Pentax J80 [a decade or so ago] and more recently the Orion ED100 and really the Orion had clearly superior images. Some of my best planetary viewing has been through the ED100. I have gone up to 240x on steady nights on Jupiter, and the amount of detail is really impressive. This is really twice the power of what the Pentax is capable of. Yes, the Pentax J80 is a classic scope that will still give you usable images but really the ED100 is clearly the best choice and in a class of its own. I have not used the Antares so cannot really comment, but it is still a long tube achro doublet. Really, the ED100 will give you easily the best viewing of the three options. A 4in. ED100 'APO' is really an impressive and cost effective scope.

On the moon, the 80/11 had significantly more violet CA than my 70/6.2 William Optics Zenithstar with FPL-51, which is an "ED" and not a true APO.

I had an Orion 100/9 ED and it was much better than the William-Optics, particularly outside focus the Z70ED had a bothersome green halo.

So... 100ED >> Z70ED >> 80/11

I can't imagine the 90/11 would have better correction than an 80/11. The 80/12 would be better than my 80/11 but not by much.

So... the 100ED f/9 will blow away all of your other options, so long as you get a good one. But most of them are, due to the long slow focal ratio.

(oh, the reason I still have the Z70ED but not the 100ED is because.. the 100ED is really long, and has a substandard focuser. I replaced it with an AT90EDT 90/6.7 - which has superior color correction to the 100ED, as it's an FPL-53 triplet, but the main reason I got it was the 2.7" rack and pinion focuser, very useful for imaging)

The irony is that I probably did it in the worst possible order - I bought the Antares, should buy the Orion based on everyone's comments, yet still want the Pentax for the 'neat' factor. Given that I want the Pentax and need the Orion, the Antares(that I already own) is probably the least needed. LOL.

I do have ED100 and 80mm achromat, not Pentax but Zeiss AS80/1200 (which was classified by Zeiss as semi-apochromat). Both scopes are wonderful. But 80mm cannot keep up with good 100mm lens as my ED100 has. This is just physics. ED100 shows more on planets, Moon, and DSO; and it is lighter and shorter. Saying that, I found myself observing more with AS80 than with ED100. May be because I obtained AS80 later than ED100. Until recently, I also had 130mm ED refractor, so when I wanted something large, I usually took out this one instead of ED100.

AS80 has one advantage, it thermalizes very quickly. ED100 is fine too with that respect. Only with 30 degrees temperature drop, it still needs about 40-50 minutes to split theta Aur. AS80 is faster: this winter I could regularly make with it a sketch of Jupiter including GRS junior and be done in 20 minutes from taking the scope outside. I tried once Vixen 130ED but that was a fiasco. I started to see GRS in about 30-35 minutes, but clouds came in 40 minutes...

I don't have any of these 'scopes, but I did publish a short CN article on side-by-side comparisons between a Meade 90 f/11 and Antares 105 f/13.

I did not see much difference in light-gathering capability, though I have been told that the effective aperture of the Antares is 96mm. Nevertheless, I don't think you will see much difference between the 90 and the 100. "Experts" may disagree.

I also did not see much difference in color between the two. Even when pushing ~400x on these 'scopes on the Moon there was just a micro-thin sliver of color around the limb. Contrast appeared to be very similar, with I think a slight nod to the Antares.

The big difference lay in their focal lengths, and the higher mags afforded by the Antares made double-splitting a lot easier. It also seemed to me that moments of steady seeing seemed "longer" in the Antares.

The 90 came out on top when it came to handling. Though the Meade is better built than the Antares and is a heavy little bugger, its shorter tube length made it easier to carry and mount.

Thanks Shane. Whether I wnd up getting 2 (Antares and Orion) or all 3, I am looking forward to doing some comparisons. My mounting capabilities are limited, so it probably won't be a side-by-side A-B, but it should be interesting nonetheless.

Just thought I'd follow up. Received the Antares scope today and it looks great. To be honest, it is quite a bit bigger than I anticipated. Not disappointed or anything - just a bit surprised. This isn't a little-league refractor. It makes me think that even if I do 'upgrade' to a 100ed, this would be an excellent scope to pass down to one of my boys at some point.

Of course, the new-scope-curse is in full effect so I won't get a chance to observe through it for quite a while given our ever-present cloud cover.

And just to prove that I am totally devoid of intelligence, I thought I'd update that I now own the Antares and the Pentax. Yep - the one scope I didn't buy was the one that most recommended. There was just something about the idea of owning an old Pentax refractor that I couldn't resist.